1 Introduction
Lake eutrophication is a process in which excessive nutrients are
accumulated in lakes, and it results from natural factors and human
activities (Zou et al. 2020). Lake eutrophication leads to the massive
growth and reproduction of algae in water column, thereby reducing the
stability of water ecosystems, and thus it has posed a global
environmental problem (Le Moal et al. 2019; David et al. 2020). At
present, the prevention and control strategies against lake
eutrophication mainly include physical, chemical, and biological ones.
Specific
technologies mainly include aeration, oxygenation, mechanical removal of
phytoplankton, dredging, and sediment removal, the addition of
flocculants and algaecides, phytoremediation (Schindler et al. 2008; Qin
et al. 2013; Niemistö et al. 2020; Zhang et al. 2020). However, it is
difficult to use physical and chemical methods for effectively solving
the problem of lake eutrophication, in contrast, biological and
ecological methods can continuously reduce pollutants in
lakes, meanwhile maintaining the
stability of the ecological environment.
Submerged
macrophytes are the main primary
producers in aquatic ecosystems and play an important role in
maintaining biodiversity and water ecosystem stability (Malecki-Brown et
al. 2010; Phillips et al. 2016).
These plants can provide habitat for
organisms, absorb nutrients from the water body and sediments, and
control sediment suspension
(Horppila and Nurminen, 2003; Veraart et al. 2011; Xian et al.
2022).
Le Bagousse-Pinguet et al. (2012)
found that interactions between submerged macrophytes can promote plant
growth and reproduction in harsh environments, and also facilitate the
growth of target macrophytes threatened by severe eutrophication.
Submerged macrophytes are also very important for improving the
eutrophication state of lakes (Gao et al. 2017).
The ability of submerged macrophytes to establish good roots in sediment
is a key element for their growth. The physical and chemical properties
of sediments play a very important role in the root growth of submerged
macrophytes (Lin et al. 2020), and they affect the process of rooting,
germinating, and stable growth of plants (Rattray et al. 1991; Xie et
al. 2005). Submerged macrophytes can also absorb nutrients directly from
the sediment to meet their own nutritional needs (Carr and Chambers.
1998). However, high contents of organic matter, nitrogen, phosphorus,
and other nutrients in eutrophication sediments accelerates the
eutrophication and water bloom (Qiu et al. 2016), thus limiting the
growth and distribution of submerged plants (Soana et al. 2012; Zhu et
al. 2016). Therefore, it is necessary to improve the sediment for the
stable growth of submerged macrophytes.
Nutrients in sediments are readily released into the water under certain
conditions (Peng et al. 2021). Addition of the substrates onto the
sediment surface can inactivate sediments and slow the release of
pollutants and nutrients from them into the water (Wang et al. 2019).
The common sediment-modifying substrates have been widely used for
ecological restoration due to their environmentally friendly nature
(Larsen et al. 2004; Liu et al. 2021). Moreover, substrate not only
affects the removal efficiency of pollutants from the water body by
aquatic plants, but also affects the growth rate of plants (Zotina et
al. 2014). Some studies have found that the substrate is the key factor
to promote the growth of submerged macrophytes (Jones et al. 2012; Xu et
al. 2016). However, there is still a lack of understanding of the links
between the substrate and the growth state of submerged macrophytes or
the sediment microenvironment.
Considering it, this study added four different kinds of commonly used
substrates to the sediment and planted Vallisneria natans (Lour.)
Hara (V. natans ). The aim of this study was to: (1) investigate
the effects of different substrates on the growth and physiological and
biochemical properties of V. natans , and (2) compare the effects
of different substrates on microorganisms in rhizosphere sediments.